To protect the eyes from bright light sources, shading techniques have been applied to optical devices such as eyewear (e.g., glasses), visors, face shields (e.g., pilot helmets) and the like. Such devices may either be made from a shaded material that constantly reduces the amount of light passing therethrough, or from a material that has an alterable shading. Photosensitive lenses change the amount of light transmitted through the entire lens equally, as do some electronically driven lenses and auto-dimming rearview mirrors in cars. The present invention is directed to those devices, referred to herein as glare-shielding glasses where small sections or regions of the device may be selectively darkened (partially or completely) so as to dim glare from a user's field of view through the device without dimming the rest of the field of view.
Glare-shielding glasses are known to exist, as demonstrated by several patents, including the following, which are also hereby incorporated by reference in their entirety for their teachings:
U.S. Pat. No. 4,848,890 to Horn, for a Visor with Sun Point Blocking, which discloses the use of a liquid crystal matrix that is used to block light in response to a photosensor;
U.S. Pat. No. 5,305,012 to Faris, for an Intelligent Electro-Optical System and Method for Automatic Glare Reduction, which teaches a method and apparatus for selectively reducing the intensity of light rays propagating towards an optical element such as an eye or a camera, including glare caused by intense sources of illumination; and
U.S. Pat. Nos. 5,671,035 and 5,841,507 to Barnes, for a Light Intensity Reduction Apparatus and Method, which discloses similar light-shielding devices, and the ability of a user to selectively set a light level threshold (user control switches), as well as a user set-up technique.
Glare-shielding glasses place darkened areas on each lens of the glasses between glare sources and the user's pupils. A photosensor built into the frames determines the direction of glare sources relative to the glasses, but the glasses must make assumptions about the positions of the user's pupils. As used in this disclosure, “glare-shield” and glare-shielding “glasses” or “surfaces” will be taken to mean any head-mounted optic through which the user views the scene before them, and includes those with temples that rest on or behind the ears as well as clip-on types that attach to other eyewear and visors that are held in front of the face (e.g., helmet visors, face shields and the like).
Furthermore, each user will place the glasses on their head in approximately the same place each time, but different users will wear the glasses somewhat differently, depending on the shape of their nose, the distance between their pupils, and other facial features. To shield all of the various positions where a user's eyes might be situated would require a large amount of the field of view to be blocked or darkened, which would hamper the usefulness of the device. Thus, the glasses need to be calibrated for each user, so that they only shadow the region occupied by one particular user's pupil positions.
Disclosed in embodiments herein is a method for calibrating a glare-shield comprising: measuring at least two relationships between a glare source and a glare calibration position; and using the measured relationships, determining the location of a darkened spot on the glare shield in response to a specific location of glare on a glare sensor.
Also disclosed in embodiments herein is a system for the calibration of glare-shielding glasses worn by a user, comprising: at least one glare source; a darkened region on the glare-shielding glasses; a user's eye for concurrently perceiving the glare source and the darkened region and adjusting the location of the darkened region relative to the glare source; a controller for determining at least a first and a second relationship between the location of the glare source, the darkened region on the glare-shielding glasses, and the user's eye; memory for recording the first and second positions of the glare source on a photodetector associated with the glare-shielding glasses when the darkened region occludes the glare source; and said controller further calculating and storing first and second calibration data points, and to calculate a correction factor therefrom and subsequently provide the glare-shielding glasses with the correction factor to adjust the position of the darkened region in response to detection of the glare source location on the photodetector.